Gut Fungi Not Found to Be Associated With Parkinson Disease

Fungi within the gut microbiome were not found to be a contributing factor in the initiation and progression of Parkinson disease (PD), according to study findings published in the Journal of Parkinson Disease.

Although the gut microbiome has been reported in prior studies to play a significant role in PD, lead study author Silke Appel-Cresswell, MD, of the Pacific Parkinson Research Centre (PPRC), and Djavad Mowafaghian, of the Centre for Brain Health and Division of Neurology, Faculty of Medicine, University of British Columbia (UBC), highlight that most existing studies have employed bacterial-specific sequencing in their analyses.

“To date, a potential role for the fungal constituents of the gut microbiome, also known as the mycobiome, has remained unexplored," said Appel-Cresswell and Mowafaghian in a statement.

Seeking to determine whether fungi within the gut mycobiome may be associated with PD, researchers utilized fungal-specific internal transcribed spacer (ITS)-2 amplicon sequencing to assess a cross-sectional cohort of 95 patients with PD and 57 controls from the PPRC at UBC.

Each participant provided a single fecal sample and completed a 2-hour study visit in which PD symptoms were examined. Samples were then filtered based on whether the sample met statistical requirements for a subsequent downstream compositional analysis.

In the analysis, the fungal mycobiome in patients with PD did not essentially differ from that found in matched controls. Moreover, no strong associations were found between gut fungi and PD symptoms, with fungal load indicated as extremely low in the participants’ fecal microbiomes.

Of the study cohort, 64 patients with PD and 42 healthy controls met the criteria for the 2-hour downstream compositional analysis. Among these samples, researchers detected virtually no fungal genomic content. Moreover, of the genera identified, most were said to originate from environmental or dietary causes.

“The data are an important piece in the puzzle of understanding the overall role of the gut microbiome in PD,” said Appel-Cresswell. “Patients with PD can rest assured that gut fungal overgrowth, or dysbiosis, is likely not a contributing factor to any of their PD symptoms, both motor and nonmotor.”

Of the fungi identified, saccharomyces were identified as the most dominant fungal genus. Notably, lower overall fungal abundance, relative to bacteria, was found in the gut microbiome of patients with PD, indicating that those with the condition may have a gut microbiome less hospitable to fungi.

"The gut microbiome in PD continues to be an exciting field of research where we are just at the beginning of unraveling potential mechanisms,” concluded Appel-Cresswell. “It will be important to publish negative results as well as positive findings along with detailed methods to have a realistic reflection of the data in the literature to accelerate discovery."

Reference

Appel-Cresswell S, Finlay BB, Kliger D, et al. The gut mycobiome in Parkinson disease. J Parkinsons Dis. Published online October 31, 2020. doi:10.3233/JPD-202237